feat(sandbox): add built-in grep and glob tools (#1784)

* feat(sandbox): add grep and glob tools

* refactor(aio-sandbox): use native file search APIs

* fix(sandbox): address review issues in grep/glob tools

- aio_sandbox: use should_ignore_path() instead of should_ignore_name()
  for include_dirs=True branch to filter nested ignored paths correctly
- aio_sandbox: add early exit when max_results reached in glob loop
- aio_sandbox: guard entry.path.startswith(path) before stripping prefix
- aio_sandbox: validate regex locally before sending to remote API
- search: skip lines exceeding max_line_chars to prevent ReDoS
- search: remove resolve() syscall in os.walk loop
- tools: avoid double get_thread_data() call in glob_tool/grep_tool
- tests: add 6 new cases covering the above code paths
- tests: patch get_app_config in truncation test to isolate config

* Fix sandbox grep/glob review feedback

* Remove unrelated Langfuse RFC from PR

backend/packages/harness/deerflow/sandbox/sandbox.py

@@ -1,5 +1,7 @@
 from abc import ABC, abstractmethod
 
+from deerflow.sandbox.search import GrepMatch
+
 
 class Sandbox(ABC):
     """Abstract base class for sandbox environments"""
@@ -61,6 +63,25 @@ class Sandbox(ABC):
         """
         pass
 
+    @abstractmethod
+    def glob(self, path: str, pattern: str, *, include_dirs: bool = False, max_results: int = 200) -> tuple[list[str], bool]:
+        """Find paths that match a glob pattern under a root directory."""
+        pass
+
+    @abstractmethod
+    def grep(
+        self,
+        path: str,
+        pattern: str,
+        *,
+        glob: str | None = None,
+        literal: bool = False,
+        case_sensitive: bool = False,
+        max_results: int = 100,
+    ) -> tuple[list[GrepMatch], bool]:
+        """Search for matches inside text files under a directory."""
+        pass
+
     @abstractmethod
     def update_file(self, path: str, content: bytes) -> None:
         """Update a file with binary content.